cxxopts.hpp

/*

Copyright (c) 2014, 2015, 2016 Jarryd Beck

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

*/

#ifndef CXX_OPTS_HPP
#define CXX_OPTS_HPP

#if defined(__GNUC__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
#endif

#include <cstring>
#include <exception>
#include <iostream>
#include <map>
#include <memory>
#include <regex>
#include <sstream>
#include <string>
#include <unordered_set>
#include <vector>

// when we ask cxxopts to use Unicode, help strings are processed using ICU,
// which results in the correct lengths being computed for strings when they
// are formatted for the help output
// it is necessary to make sure that <unicode/unistr.h> can be found by the
// compiler, and that icu-uc is linked in to the binary.

#ifdef CXXOPTS_USE_UNICODE
#include <unicode/unistr.h>

namespace cxxopts
{
  typedef icu::UnicodeString String;

  inline String
  toLocalString(std::string s)
  {
    return icu::UnicodeString::fromUTF8(s);
  }

  class UnicodeStringIterator : public std::iterator<std::forward_iterator_tag, int32_t>
  {
   public:
    UnicodeStringIterator(const icu::UnicodeString* s, int32_t pos) : s(s), i(pos)
    {
    }

    value_type operator*() const
    {
      return s->char32At(i);
    }

    bool
    operator==(const UnicodeStringIterator& rhs) const
    {
      return s == rhs.s && i == rhs.i;
    }

    bool
    operator!=(const UnicodeStringIterator& rhs) const
    {
      return !(*this == rhs);
    }

    UnicodeStringIterator& operator++()
    {
      ++i;
      return *this;
    }

    UnicodeStringIterator
    operator+(int32_t v)
    {
      return UnicodeStringIterator(s, i + v);
    }

   private:
    const icu::UnicodeString* s;
    int32_t                   i;
  };

  inline String&
  stringAppend(String& s, String a)
  {
    return s.append(std::move(a));
  }

  inline String&
  stringAppend(String& s, int n, UChar32 c)
  {
    for (int i = 0; i != n; ++i)
    {
      s.append(c);
    }

    return s;
  }

  template <typename Iterator>
  String&
  stringAppend(String& s, Iterator begin, Iterator end)
  {
    while (begin != end)
    {
      s.append(*begin);
      ++begin;
    }

    return s;
  }

  inline size_t
  stringLength(const String& s)
  {
    return s.length();
  }

  inline std::string
  toUTF8String(const String& s)
  {
    std::string result;
    s.toUTF8String(result);

    return result;
  }

  inline bool
  empty(const String& s)
  {
    return s.isEmpty();
  }
}

namespace std
{
  cxxopts::UnicodeStringIterator
  begin(const icu::UnicodeString& s)
  {
    return cxxopts::UnicodeStringIterator(&s, 0);
  }

  cxxopts::UnicodeStringIterator
  end(const icu::UnicodeString& s)
  {
    return cxxopts::UnicodeStringIterator(&s, s.length());
  }
}

// ifdef CXXOPTS_USE_UNICODE
#else

namespace cxxopts
{
  typedef std::string String;

  template <typename T>
  T
  toLocalString(T&& t)
  {
    return t;
  }

  inline size_t
  stringLength(const String& s)
  {
    return s.length();
  }

  inline String&
  stringAppend(String& s, String a)
  {
    return s.append(std::move(a));
  }

  inline String&
  stringAppend(String& s, size_t n, char c)
  {
    return s.append(n, c);
  }

  template <typename Iterator>
  String&
  stringAppend(String& s, Iterator begin, Iterator end)
  {
    return s.append(begin, end);
  }

  template <typename T>
  std::string
  toUTF8String(T&& t)
  {
    return std::forward<T>(t);
  }

  inline bool
  empty(const std::string& s)
  {
    return s.empty();
  }
}

// ifdef CXXOPTS_USE_UNICODE
#endif

namespace cxxopts
{
  class Value : public std::enable_shared_from_this<Value>
  {
   public:
    virtual void parse(const std::string& text) const = 0;

    virtual void parse() const = 0;

    virtual bool has_arg() const = 0;

    virtual bool has_default() const = 0;

    virtual bool is_container() const = 0;

    virtual bool has_implicit() const = 0;

    virtual std::string get_default_value() const = 0;

    virtual std::string get_implicit_value() const = 0;

    virtual std::shared_ptr<Value> default_value(const std::string& value) = 0;

    virtual std::shared_ptr<Value> implicit_value(const std::string& value) = 0;
  };

  class OptionException : public std::exception
  {
   public:
    OptionException(const std::string& message) : m_message(message)
    {
    }

    virtual const char*
    what() const noexcept
    {
      return m_message.c_str();
    }

   private:
    std::string m_message;
  };

  class OptionSpecException : public OptionException
  {
   public:
    OptionSpecException(const std::string& message) : OptionException(message)
    {
    }
  };

  class OptionParseException : public OptionException
  {
   public:
    OptionParseException(const std::string& message) : OptionException(message)
    {
    }
  };

  class option_exists_error : public OptionSpecException
  {
   public:
    option_exists_error(const std::string& option) : OptionSpecException(u8"Option ‘" + option + u8"’ already exists")
    {
    }
  };

  class invalid_option_format_error : public OptionSpecException
  {
   public:
    invalid_option_format_error(const std::string& format)
        : OptionSpecException(u8"Invalid option format ‘" + format + u8"’")
    {
    }
  };

  class option_not_exists_exception : public OptionParseException
  {
   public:
    option_not_exists_exception(const std::string& option)
        : OptionParseException(u8"Option ‘" + option + u8"’ does not exist")
    {
    }
  };

  class missing_argument_exception : public OptionParseException
  {
   public:
    missing_argument_exception(const std::string& option)
        : OptionParseException(u8"Option ‘" + option + u8"’ is missing an argument")
    {
    }
  };

  class option_requires_argument_exception : public OptionParseException
  {
   public:
    option_requires_argument_exception(const std::string& option)
        : OptionParseException(u8"Option ‘" + option + u8"’ requires an argument")
    {
    }
  };

  class option_not_has_argument_exception : public OptionParseException
  {
   public:
    option_not_has_argument_exception(const std::string& option, const std::string& arg)
        : OptionParseException(u8"Option ‘" + option + u8"’ does not take an argument, but argument‘" + arg + "’ given")
    {
    }
  };

  class option_not_present_exception : public OptionParseException
  {
   public:
    option_not_present_exception(const std::string& option)
        : OptionParseException(u8"Option ‘" + option + u8"’ not present")
    {
    }
  };

  class argument_incorrect_type : public OptionParseException
  {
   public:
    argument_incorrect_type(const std::string& arg) : OptionParseException(u8"Argument ‘" + arg + u8"’ failed to parse")
    {
    }
  };

  namespace values
  {
    template <typename T>
    void
    parse_value(const std::string& text, T& value)
    {
      std::istringstream is(text);
      if (!(is >> value))
      {
        throw argument_incorrect_type(text);
      }

      if (is.rdbuf()->in_avail() != 0)
      {
        throw argument_incorrect_type(text);
      }
    }

    inline void
    parse_value(const std::string& /*text*/, bool& value)
    {
      // TODO recognise on, off, yes, no, enable, disable
      // so that we can write --long=yes explicitly
      value = true;
    }

    inline void
    parse_value(const std::string& text, std::string& value)
    {
      value = text;
    }

    template <typename T>
    void
    parse_value(const std::string& text, std::vector<T>& value)
    {
      T v;
      parse_value(text, v);
      value.push_back(v);
    }

    template <typename T>
    struct value_has_arg
    {
      static constexpr bool value = true;
    };

    template <>
    struct value_has_arg<bool>
    {
      static constexpr bool value = false;
    };

    template <typename T>
    struct type_is_container
    {
      static constexpr bool value = false;
    };

    template <typename T>
    struct type_is_container<std::vector<T>>
    {
      static constexpr bool value = true;
    };

    template <typename T>
    class standard_value : public Value
    {
     public:
      standard_value() : m_result(std::make_shared<T>()), m_store(m_result.get())
      {
      }

      standard_value(T* t) : m_store(t)
      {
      }

      void
      parse(const std::string& text) const
      {
        if (m_implicit && text.empty())
        {
          parse_value(m_implicit_value, *m_store);
        }
        else
        {
          parse_value(text, *m_store);
        }
      }

      bool
      is_container() const
      {
        return type_is_container<T>::value;
      }

      void
      parse() const
      {
        parse_value(m_default_value, *m_store);
      }

      bool
      has_arg() const
      {
        return value_has_arg<T>::value;
      }

      bool
      has_default() const
      {
        return m_default;
      }

      bool
      has_implicit() const
      {
        return m_implicit;
      }

      virtual std::shared_ptr<Value>
      default_value(const std::string& value)
      {
        m_default       = true;
        m_default_value = value;
        return shared_from_this();
      }

      virtual std::shared_ptr<Value>
      implicit_value(const std::string& value)
      {
        m_implicit       = true;
        m_implicit_value = value;
        return shared_from_this();
      }

      std::string
      get_default_value() const
      {
        return m_default_value;
      }

      std::string
      get_implicit_value() const
      {
        return m_implicit_value;
      }

      const T&
      get() const
      {
        if (m_store == nullptr)
        {
          return *m_result;
        }
        else
        {
          return *m_store;
        }
      }

     protected:
      std::shared_ptr<T> m_result;
      T*                 m_store;
      bool               m_default = false;
      std::string        m_default_value;
      bool               m_implicit = false;
      std::string        m_implicit_value;
    };
  }

  template <typename T>
  std::shared_ptr<Value>
  value()
  {
    return std::make_shared<values::standard_value<T>>();
  }

  template <typename T>
  std::shared_ptr<Value>
  value(T& t)
  {
    return std::make_shared<values::standard_value<T>>(&t);
  }

  class OptionAdder;

  class OptionDetails
  {
   public:
    OptionDetails(const String& description, std::shared_ptr<const Value> value)
        : m_desc(description), m_value(value), m_count(0)
    {
    }

    const String&
    description() const
    {
      return m_desc;
    }

    bool
    has_arg() const
    {
      return m_value->has_arg();
    }

    void
    parse(const std::string& text)
    {
      m_value->parse(text);
      ++m_count;
    }

    void
    parse_default()
    {
      m_value->parse();
    }

    int
    count() const
    {
      return m_count;
    }

    const Value&
    value() const
    {
      return *m_value;
    }

    template <typename T>
    const T&
    as() const
    {
#ifdef CXXOPTS_NO_RTTI
      return static_cast<const values::standard_value<T>&>(*m_value).get();
#else
      return dynamic_cast<const values::standard_value<T>&>(*m_value).get();
#endif
    }

   private:
    String                       m_desc;
    std::shared_ptr<const Value> m_value;
    int                          m_count;
  };

  struct HelpOptionDetails
  {
    std::string s;
    std::string l;
    String      desc;
    bool        has_arg;
    bool        has_default;
    std::string default_value;
    bool        has_implicit;
    std::string implicit_value;
    std::string arg_help;
    bool        is_container;
  };

  struct HelpGroupDetails
  {
    std::string                    name;
    std::string                    description;
    std::vector<HelpOptionDetails> options;
  };

  class Options
  {
   public:
    Options(std::string program, std::string help_string = "")
        : m_program(std::move(program))
        , m_help_string(toLocalString(std::move(help_string)))
        , m_positional_help("positional parameters")
        , m_next_positional(m_positional.end())
    {
    }

    inline Options&
    positional_help(const std::string& help_text)
    {
      m_positional_help = std::move(help_text);
      return *this;
    }

    inline void parse(int& argc, char**& argv);

    inline OptionAdder add_options(std::string group = "");

    inline void add_option(const std::string&           group,
                           const std::string&           s,
                           const std::string&           l,
                           std::string                  desc,
                           std::shared_ptr<const Value> value,
                           std::string                  arg_help);

    int
    count(const std::string& o) const
    {
      auto iter = m_options.find(o);
      if (iter == m_options.end())
      {
        return 0;
      }

      return iter->second->count();
    }

    const OptionDetails& operator[](const std::string& option) const
    {
      auto iter = m_options.find(option);

      if (iter == m_options.end())
      {
        throw option_not_present_exception(option);
      }

      return *iter->second;
    }

    // parse positional arguments into the given option
    inline void parse_positional(std::string option);

    inline void parse_positional(std::vector<std::string> options);

    inline std::string help(const std::vector<std::string>& groups = {""}) const;

    inline const std::vector<std::string> groups() const;

    inline const HelpGroupDetails& group_help(const std::string& group) const;

   private:
    inline void add_one_option(const std::string& option, std::shared_ptr<OptionDetails> details);

    inline bool consume_positional(std::string a);

    inline void add_to_option(const std::string& option, const std::string& arg);

    inline void parse_option(std::shared_ptr<OptionDetails> value,
                             const std::string&             name,
                             const std::string&             arg = "");

    inline void checked_parse_arg(
        int argc, char* argv[], int& current, std::shared_ptr<OptionDetails> value, const std::string& name);

    inline String help_one_group(const std::string& group) const;

    std::string m_program;
    String      m_help_string;
    std::string m_positional_help;

    std::map<std::string, std::shared_ptr<OptionDetails>> m_options;
    std::vector<std::string>           m_positional;
    std::vector<std::string>::iterator m_next_positional;
    std::unordered_set<std::string>    m_positional_set;

    // mapping from groups to help options
    std::map<std::string, HelpGroupDetails> m_help;
  };

  class OptionAdder
  {
   public:
    OptionAdder(Options& options, std::string group) : m_options(options), m_group(std::move(group))
    {
    }

    inline OptionAdder& operator()(const std::string&           opts,
                                   const std::string&           desc,
                                   std::shared_ptr<const Value> value    = ::cxxopts::value<bool>(),
                                   std::string                  arg_help = "");

   private:
    Options&    m_options;
    std::string m_group;
  };
}

namespace cxxopts
{

  namespace
  {

    constexpr int OPTION_LONGEST  = 30;
    constexpr int OPTION_DESC_GAP = 2;

    std::basic_regex<char> option_matcher("--([[:alnum:]][-_[:alnum:]]+)(=(.*))?|-([[:alnum:]]+)");

    std::basic_regex<char> option_specifier("(([[:alnum:]]),)?([[:alnum:]][-_[:alnum:]]+)");

    String
    format_option(const HelpOptionDetails& o)
    {
      auto& s = o.s;
      auto& l = o.l;

      String result = "  ";

      if (s.size() > 0)
      {
        result += "-" + toLocalString(s) + ",";
      }
      else
      {
        result += "   ";
      }

      if (l.size() > 0)
      {
        result += " --" + toLocalString(l);
      }

      if (o.has_arg)
      {
        auto arg = o.arg_help.size() > 0 ? toLocalString(o.arg_help) : "arg";

        if (o.has_implicit)
        {
          result += " [=" + arg + "(=" + toLocalString(o.implicit_value) + ")]";
        }
        else
        {
          result += " " + arg;
        }
      }

      return result;
    }

    String
    format_description(const HelpOptionDetails& o, size_t start, size_t width)
    {
      auto desc = o.desc;

      if (o.has_default)
      {
        desc += toLocalString(" (default: " + o.default_value + ")");
      }

      String result;

      auto current   = std::begin(desc);
      auto startLine = current;
      auto lastSpace = current;

      auto size = size_t{};

      while (current != std::end(desc))
      {
        if (*current == ' ')
        {
          lastSpace = current;
        }

        if (size > width)
        {
          if (lastSpace == startLine)
          {
            stringAppend(result, startLine, current + 1);
            stringAppend(result, "\n");
            stringAppend(result, start, ' ');
            startLine = current + 1;
            lastSpace = startLine;
          }
          else
          {
            stringAppend(result, startLine, lastSpace);
            stringAppend(result, "\n");
            stringAppend(result, start, ' ');
            startLine = lastSpace + 1;
          }
          size = 0;
        }
        else
        {
          ++size;
        }

        ++current;
      }

      // append whatever is left
      stringAppend(result, startLine, current);

      return result;
    }
  }

  OptionAdder
  Options::add_options(std::string group)
  {
    return OptionAdder(*this, std::move(group));
  }

  OptionAdder&
  OptionAdder::operator()(const std::string&           opts,
                          const std::string&           desc,
                          std::shared_ptr<const Value> value,
                          std::string                  arg_help)
  {
    std::match_results<const char*> result;
    std::regex_match(opts.c_str(), result, option_specifier);

    if (result.empty())
    {
      throw invalid_option_format_error(opts);
    }

    const auto& s = result[2];
    const auto& l = result[3];

    m_options.add_option(m_group, s.str(), l.str(), desc, value, std::move(arg_help));

    return *this;
  }

  void
  Options::parse_option(std::shared_ptr<OptionDetails> value, const std::string& /*name*/, const std::string& arg)
  {
    value->parse(arg);
  }

  void
  Options::checked_parse_arg(
      int argc, char* argv[], int& current, std::shared_ptr<OptionDetails> value, const std::string& name)
  {
    if (current + 1 >= argc)
    {
      if (value->value().has_implicit())
      {
        parse_option(value, name, "");
      }
      else
      {
        throw missing_argument_exception(name);
      }
    }
    else
    {
      if (argv[current + 1][0] == '-' && value->value().has_implicit())
      {
        parse_option(value, name, "");
      }
      else
      {
        parse_option(value, name, argv[current + 1]);
        ++current;
      }
    }
  }

  void
  Options::add_to_option(const std::string& option, const std::string& arg)
  {
    auto iter = m_options.find(option);

    if (iter == m_options.end())
    {
      throw option_not_exists_exception(option);
    }

    parse_option(iter->second, option, arg);
  }

  bool
  Options::consume_positional(std::string a)
  {
    while (m_next_positional != m_positional.end())
    {
      auto iter = m_options.find(*m_next_positional);
      if (iter != m_options.end())
      {
        if (!iter->second->value().is_container())
        {
          if (iter->second->count() == 0)
          {
            add_to_option(*m_next_positional, a);
            ++m_next_positional;
            return true;
          }
          else
          {
            ++m_next_positional;
            continue;
          }
        }
        else
        {
          add_to_option(*m_next_positional, a);
          return true;
        }
      }
      ++m_next_positional;
    }

    return false;
  }

  void
  Options::parse_positional(std::string option)
  {
    parse_positional(std::vector<std::string>{option});
  }

  void
  Options::parse_positional(std::vector<std::string> options)
  {
    m_positional      = std::move(options);
    m_next_positional = m_positional.begin();

    m_positional_set.insert(m_positional.begin(), m_positional.end());
  }

  void
  Options::parse(int& argc, char**& argv)
  {
    int current = 1;

    int nextKeep = 1;

    bool consume_remaining = false;

    while (current != argc)
    {
      if (strcmp(argv[current], "--") == 0)
      {
        consume_remaining = true;
        ++current;
        break;
      }

      std::match_results<const char*> result;
      std::regex_match(argv[current], result, option_matcher);

      if (result.empty())
      {
        // not a flag

        // if true is returned here then it was consumed, otherwise it is
        // ignored
        if (consume_positional(argv[current]))
        {
        }
        else
        {
          argv[nextKeep] = argv[current];
          ++nextKeep;
        }
        // if we return from here then it was parsed successfully, so continue
      }
      else
      {
        // short or long option?
        if (result[4].length() != 0)
        {
          const std::string& s = result[4];

          for (std::size_t i = 0; i != s.size(); ++i)
          {
            std::string name(1, s[i]);
            auto        iter = m_options.find(name);

            if (iter == m_options.end())
            {
              throw option_not_exists_exception(name);
            }

            auto value = iter->second;

            // if no argument then just add it
            if (!value->has_arg())
            {
              parse_option(value, name);
            }
            else
            {
              // it must be the last argument
              if (i + 1 == s.size())
              {
                checked_parse_arg(argc, argv, current, value, name);
              }
              else if (value->value().has_implicit())
              {
                parse_option(value, name, "");
              }
              else
              {
                // error
                throw option_requires_argument_exception(name);
              }
            }
          }
        }
        else if (result[1].length() != 0)
        {
          const std::string& name = result[1];

          auto iter = m_options.find(name);

          if (iter == m_options.end())
          {
            throw option_not_exists_exception(name);
          }

          auto opt = iter->second;

          // equals provided for long option?
          if (result[3].length() != 0)
          {
            // parse the option given

            // but if it doesn't take an argument, this is an error
            if (!opt->has_arg())
            {
              throw option_not_has_argument_exception(name, result[3]);
            }

            parse_option(opt, name, result[3]);
          }
          else
          {
            if (opt->has_arg())
            {
              // parse the next argument
              checked_parse_arg(argc, argv, current, opt, name);
            }
            else
            {
              // parse with empty argument
              parse_option(opt, name);
            }
          }
        }
      }

      ++current;
    }

    for (auto& opt : m_options)
    {
      auto& detail = opt.second;
      auto& value  = detail->value();

      if (!detail->count() && value.has_default())
      {
        detail->parse_default();
      }
    }

    if (consume_remaining)
    {
      while (current < argc)
      {
        consume_positional(argv[current]);
        ++current;
      }
    }

    argc = nextKeep;
  }

  void
  Options::add_option(const std::string&           group,
                      const std::string&           s,
                      const std::string&           l,
                      std::string                  desc,
                      std::shared_ptr<const Value> value,
                      std::string                  arg_help)
  {
    auto stringDesc = toLocalString(std::move(desc));
    auto option     = std::make_shared<OptionDetails>(stringDesc, value);

    if (s.size() > 0)
    {
      add_one_option(s, option);
    }

    if (l.size() > 0)
    {
      add_one_option(l, option);
    }

    // add the help details
    auto& options = m_help[group];

    options.options.emplace_back(HelpOptionDetails{s,
                                                   l,
                                                   stringDesc,
                                                   value->has_arg(),
                                                   value->has_default(),
                                                   value->get_default_value(),
                                                   value->has_implicit(),
                                                   value->get_implicit_value(),
                                                   std::move(arg_help),
                                                   value->is_container()});
  }

  void
  Options::add_one_option(const std::string& option, std::shared_ptr<OptionDetails> details)
  {
    auto in = m_options.emplace(option, details);

    if (!in.second)
    {
      throw option_exists_error(option);
    }
  }

  String
  Options::help_one_group(const std::string& g) const
  {
    typedef std::vector<std::pair<String, String>> OptionHelp;

    auto group = m_help.find(g);
    if (group == m_help.end())
    {
      return "";
    }

    OptionHelp format;

    size_t longest = 0;

    String result;

    if (!g.empty())
    {
      result += toLocalString(" " + g + " options:\n");
    }

    for (const auto& o : group->second.options)
    {
      if (o.is_container && m_positional_set.find(o.l) != m_positional_set.end())
      {
        continue;
      }

      auto s  = format_option(o);
      longest = std::max(longest, stringLength(s));
      format.push_back(std::make_pair(s, String()));
    }

    longest = std::min(longest, static_cast<size_t>(OPTION_LONGEST));

    // widest allowed description
    auto allowed = size_t{76} - longest - OPTION_DESC_GAP;

    auto fiter = format.begin();
    for (const auto& o : group->second.options)
    {
      if (o.is_container && m_positional_set.find(o.l) != m_positional_set.end())
      {
        continue;
      }

      auto d = format_description(o, longest + OPTION_DESC_GAP, allowed);

      result += fiter->first;
      if (stringLength(fiter->first) > longest)
      {
        result += '\n';
        result += toLocalString(std::string(longest + OPTION_DESC_GAP, ' '));
      }
      else
      {
        result += toLocalString(std::string(longest + OPTION_DESC_GAP - stringLength(fiter->first), ' '));
      }
      result += d;
      result += '\n';

      ++fiter;
    }

    return result;
  }

  std::string
  Options::help(const std::vector<std::string>& groups) const
  {
    String result = m_help_string + "\nUsage:\n  " + toLocalString(m_program) + " [OPTION...]";

    if (m_positional.size() > 0)
    {
      result += " " + toLocalString(m_positional_help);
    }

    result += "\n\n";

    for (std::size_t i = 0; i < groups.size(); ++i)
    {
      String const& group_help = help_one_group(groups[i]);
      if (empty(group_help))
        continue;
      result += group_help;
      if (i < groups.size() - 1)
      {
        result += '\n';
      }
    }

    return toUTF8String(result);
  }

  const std::vector<std::string>
  Options::groups() const
  {
    std::vector<std::string> g;

    std::transform(m_help.begin(),
                   m_help.end(),
                   std::back_inserter(g),
                   [](const std::map<std::string, HelpGroupDetails>::value_type& pair) { return pair.first; });

    return g;
  }

  const HelpGroupDetails&
  Options::group_help(const std::string& group) const
  {
    return m_help.at(group);
  }
}

#if defined(__GNU__)
#pragma GCC diagnostic pop
#endif

#endif  // CXX_OPTS_HPP